char: serial: check divider value against baud base

Commit Message

Prasad Pandit Oct. 11, 2016, 4:27 p.m. UTC

From: Prasad J Pandit <[e-mail]>

16550A UART device uses an oscillator to generate frequencies
(baud base), which decide communication speed. This speed could
be changed by dividing it by a divider. If the divider is
greater than the baud base, speed is set to zero, leading to a
divide by zero error. Add check to avoid it.

Reported-by: Huawei PSIRT <[e-mail]>
Signed-off-by: Prasad J Pandit <[e-mail]>
---
 hw/char/serial.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

[e-mail] Oct. 12, 2016, 12:57 a.m. UTC | #1

Hi,

Your series seems to have some coding style problems. See output below for
more information:

Subject: [Qemu-devel] [PATCH] char: serial: check divider value against baud base
Message-id: [e-mail]
Type: series

=== TEST SCRIPT BEGIN ===
#!/bin/bash

BASE=base
n=1
total=$(git log --oneline $BASE.. | wc -l)
failed=0

# Useful git options
git config --local diff.renamelimit 0
git config --local diff.renames True

commits="$(git log --format=%H --reverse $BASE..)"
for c in $commits; do
    echo "Checking PATCH $n/$total: $(git show --no-patch --format=%s $c)..."
    if ! git show $c --format=email | ./scripts/checkpatch.pl --mailback -; then
        failed=1
        echo
    fi
    n=$((n+1))
done

exit $failed
=== TEST SCRIPT END ===

Updating 3c8cf5a9c21ff8782164d1def7f44bd888713384
Switched to a new branch 'test'
7aea007 char: serial: check divider value against baud base

=== OUTPUT BEGIN ===
Checking PATCH 1/1: char: serial: check divider value against baud base...
ERROR: braces {} are necessary for all arms of this statement
#25: FILE: hw/char/serial.c:156:
+    if (s->divider == 0 || s->divider > s->baudbase)
[...]

total: 1 errors, 0 warnings, 8 lines checked

Your patch has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.

=== OUTPUT END ===

Test command exited with code: 1


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Prasad Pandit Oct. 12, 2016, 6:07 a.m. UTC | #2

+-- On Tue, 11 Oct 2016, [e-mail] wrote --+
| Your series seems to have some coding style problems.
| === OUTPUT BEGIN ===
| Checking PATCH 1/1: char: serial: check divider value against baud base...
| ERROR: braces {} are necessary for all arms of this statement
| #25: FILE: hw/char/serial.c:156:
| +    if (s->divider == 0 || s->divider > s->baudbase)
| [...]
| 
| Your patch has style problems, please review.

Ah sorry, I've sent a corrected patch v2.
--
Prasad J Pandit / Red Hat Product Security Team
47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F

Patch

diff --git a/hw/char/serial.c b/hw/char/serial.c
index 3442f47..f659bbd 100644
--- a/hw/char/serial.c
+++ b/hw/char/serial.c
@@ -153,7 +153,7 @@  static void serial_update_parameters(SerialState *s)
     int speed, parity, data_bits, stop_bits, frame_size;
     QEMUSerialSetParams ssp;
 
-    if (s->divider == 0)
+    if (s->divider == 0 || s->divider > s->baudbase)
         return;
 
     /* Start bit. */